Most folding knives incorporate some kind of a mechanism that holds the blade or working implement safely in the closed position in which the sharp edge of the blade is held safely within the handle. There are many known mechanisms for retaining blades in the closed position, and there are obvious reasons why such mechanisms are used. Among other reasons, blade-retaining mechanisms prevent unintended opening of the knife and thus promote safety.
Automatic opening mechanisms and so-called “opening assist” mechanisms may be incorporated into folding knives. Generally speaking, in a knife that has an automatic opening mechanism the blade is held in the closed position by a latched trigger mechanism. When closed, the blade is under a constant “pre-load” pressure from a spring mechanism. When the trigger is released, the blade is automatically driven by the spring mechanism into the open position. On the other hand, with knives that incorporate opening assist mechanisms the blade is retained in the closed position without the need for a latch or trigger. The opening assist function is provided by a spring mechanism that operates on the blade. As the user manually rotates the blade from closed toward the open position, the spring mechanism that acts on the blade reaches a threshold point or top-dead-center point. After the blade rotates beyond the threshold point the spring drives the blade to the open position. Opening assist knives are also often called “semi-automatic” knives.
Both knives equipped with automatic and opening assist mechanisms typically include some kind of locking mechanism to lock the blade open, and with many opening assist knives the same spring mechanism that drives the blade open also retains the blade closed.
For a variety of reasons, opening assist mechanisms are becoming very popular. For example, in appropriate circumstances and for appropriate users, there are many advantages to be derived from semi-automatic opening knives and many situations where automatic knives can be useful. These often include situations where the user has only one hand free. However, even in a knife that includes an automated opening or opening assist mechanism, safety considerations always mandate that the blade stays in the closed position until the user volitionally and intentionally moves the blade into the open position. For example, a mechanism that holds a knife blade closed should never release when the knife is dropped. With the recent increases in popularity of opening assist knives there are many new types of mechanisms being developed.
There is always a need however for mechanisms that provide an automatic or semi-automatic opening feature for knives.
The present invention comprises folding knife having an opening assist mechanism that may be either automatic or of the type more typically called opening assist styles. It will be appreciated that in the present discussion the term “opening assist” mechanism refers to a mechanism that may be used with either an automatic knife or a semi-automatic knife; both types of knives are detailed below and shown in the drawings. The mechanism of the present invention uses a pair of spring arms, one on each lateral side of the blade and interconnected at their free ends with a pin to apply pressure to the blade to drive it to the open position. An automatic knife using the mechanism of the present invention has a differently configured blade where the pin acts on the blade from an opening assist knife that incorporates the mechanism. With respect to the opening assist functionality used in a semi-automatic knife, once a threshold point in the rotational movement of the blade is passed as the blade is moved from the closed toward the open position, the mechanism of the present invention rotationally drives the blade into the fully open position. This is accomplished with the paired spring arms acting through the interconnecting roller pin, which acts on the blade and thereby imparts sufficient rotational kinetic energy to the blade that the inertia drives the blade into the fully open position. A locking mechanism locks the blade in the open position.